Advanced analytical techniques are towards micro-analyzers with advantages of small sample requirement, reduced assay time, low manufacturing cost, and portable flexibility. Up to date, immunoassay is still the main stream in the clinical diagnostic methods and is widely used in various selective and sensitive detections of small and large molecules through specific bindings of antibody and antigen. The research and development of immunoassay continues to fuel up by the high demand of the society for health care quality, food quality control, monitoring and biological security. With current progress in versatile, inexpensive, and reliable techniques for microfabrication and bio-interaction, antibody microarrays and microfluidic immunosensors, or their combinations bring about new generation of powerful analytical tools for important applications in proteomics, drug discovery and diagnostics.
Most of the early devices used for such methods were made using silicon and glass as the substrates, since their microfabrication including patterning, etching and bonding can directly borrow the matured technology from the semiconductor industry. As an economic alternative, polymer substrate was employed to fabricate the microfluidic device by simple molding instead of the expensive patterning process used in semiconductor industry. However, the surface properties of the polymer microdevices are varied due to diversity of the physical and chemical properties of the polymeric materials in use.
For example, microfluidic immunoassay devices have been made with for example with poly(dimethylsiloxane) (PDMS). PDMS as an economic alternative is one of the polymer substrates mostly used due to its high cast fidelity in a mold. However, its resin takes a long time (a number of hours) to cure, and the device has strong non-specific interference caused by its hydrophobic nature. Thus, surface modification is usually a must to improve protein probe attachment and eliminate non-specific adsorption. Additionally, the polymer microfluidic device so far needs a complicated manufacture process to fabricate its 3D patterned structure including master microfabrication, polymer structure molding and surface modification.
Thus, it is an object of the present invention to provide alternative fabrication methods for microdevices which can be used for example for chemical and/or biological assays and which require reduced surface modification for the binding of certain molecules.